Classification and Dichotomous Keys

Directions for using the dichotomous key for fish identification

1. Look at butterflyfish “M” on your Dichotomous Key Worksheet.
2. Using the Butterflyfish dichotomous key, identify butterflyfish “M” by following these example steps:
   1. Starting at decision point 1, read the two statements describing a certain feature of the butterflyfish.
   2. Decide which statement fits the picture of your fish. For example, the description, “Pelvic fin dark,” is the correct description for butterflyfish “M.” Refer to the diagram for generalized fish anatomy.
   3. Note the number to the right side of this statement. It is #2.
   4. Go to the #2 decision point as indicated by your choice in the first decision point, and again decide which statement better describes the fish. Here, the second statement, “Lacks two large white spots below dorsal fin,” is the correct choice.
   5. Note the number on the right side of this statement. It is #3.
   6. Proceed to the #3 decision point as indicated by the previous decision point.
   7. Again, decide which statement better describes the fish on your card. Between the two choices at the #3 decision point, “Tail with one dark bar at tip,” is the better choice. This decision identifies butterflyfish “M” with its correct scientific name: Chaetodon kleini.
   8. Record the name of your fish below its picture on the Dichotomous Key Worksheet. (Because all fish to be identified are in the genus Chaetodon, the name of the genus may be abbreviated as “C.” For example, Chaetodon kleini may be identified as C. kleini).
3. Identify all of the butterflyfish on the Dichotomous Key Worksheet.
   1. Read the two descriptions at each decision point, then select the description that better matches the fish.
   2. Repeat the process, selecting the proper description and following the decision points indicated until you reach a choice that provides the identification of the fish.
   3. When you identify a fish, write its scientific name under its image.
   4. Continue until you identify all of the fish on the Worksheet.
   5. Put all of your answer into the Google Form and check your answers.